Apparatuses and methods for structurally replacing cracked welds in nuclear power plants

ABSTRACT

An apparatus configured to structurally replace a cracked weld in a nuclear plant may include: a first body portion that includes a first gripping portion; a second body portion that includes a second gripping portion; a wedge portion between the first and second body portions; and/or an adjustment portion. The first body portion may be configured to slidably engage the second body portion. The wedge portion may be configured to exert force on the slidably engaged first and second body portions. The adjustment portion may be configured to increase or decrease the force exerted by the wedge portion on the slidably engaged first and second body portions. When the adjustment portion increases the force exerted by the wedge portion on the slidably engaged first and second body portions, a distance between the first and second gripping portions may decrease.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of, and claims priority under 35 U.S.C. § 120 to,U.S. application Ser. No. 15/481,788, filed Apr. 7, 2017, which is adivisional of, and claims priority under 35 U.S.C. § 120 to, U.S.application Ser. No. 14/184,884, filed Feb. 20, 2014. The entirecontents of each of which are hereby incorporated herein by reference.

BACKGROUND 1. Field

Example embodiments generally relate to apparatuses and methods forstructurally replacing cracked welds. Example embodiments also relate tonuclear power plants and to apparatuses and methods for structurallyreplacing cracked welds of the nuclear power plants.

2. Description of Related Art

In many applications, such as nuclear reactors, steam driven turbines,or water deaerators, high-temperature water may adversely affect theassociated structures by contributing to stress corrosion cracks,corrosion, erosion, and so forth. For example, high temperature watersmay contribute to stress corrosion cracking (“SCC”) in materials, suchas carbon steels, alloy steels, stainless steels, nickel-based alloys,cobalt-based alloys, and zirconium-based alloys. SCC may preferentiallyoccur with certain combinations of alloys, environment, and stress.

As would be understood by a person having ordinary skill in the art(“PHOSITA”), SCC may include cracks propagated by static or dynamictensile stresses acting in combination with corrosion at crack tips.These stresses may result or originate from differences in thermalexpansion or contraction between components, relatively high or varyingoperating pressures, or various processes performed during themanufacture and assembly of the components or system. For example,residual stresses often result from cold working, grinding, machining,and other thermo-mechanical metal treatments. Water chemistry, welding,heat treatment, and radiation may also increase the susceptibility ofmetal or alloy component to SCC. SCC may be transgranular orintergranular in nature.

SCC may occur at greater rates under various conditions, such as thepresence of oxygen, high radiation flux, and so forth. In nuclearreactors such as a pressurized water reactor (“PWR”) or a boiling waterreactor (“BWR”), high radiation flux may cause radiolytic decompositionof the reactor coolant (water); this decomposition may produce oxygen,hydrogen peroxide, short-lived radicals, and various oxidizing species.These products of radiolytic decomposition may promote SCC in thevarious system components, such as pipes, pumps, valves, turbines, andso forth. Operating temperature and pressure for a BWR may be about 300°C. and about 10 MPa, and those for a PWR may be about 325° C. and about15 MPa. Thus, the operating environment for BWRs and PWRs may increasethe risk of having SCC issues in nuclear reactor components.

The microstructure of metals and alloys may include grains separated bygrain boundaries. Intergranular stress corrosion cracking (“IGSCC”) maybe a more localized SCC attack along or adjacent to grain boundaries,with the bulk of the grains themselves remaining largely unaffected.IGSCC may be associated with chemical segregation effects (e.g.,impurity enrichment at grain boundaries) or with specific phasesprecipitated at grain boundaries.

Irradiation assisted stress corrosion cracking (“IASCC”) may refer toacceleration of SCC by irradiation (e.g., irradiation-induced changesthat may involve microstructure changes, microchemical changes, andcompositional changes by transmutation). IASCC may result from theeffects of beta radiation, gamma radiation, neutron radiation, or otherparticle radiation (e.g., ions). However, for BWRs and PWRs, IASCC maybe primarily due to neutron radiation.

Due to the serious nature of IASCC, the Nuclear Regulatory Commission(“NRC”) commissioned a series of studies over about a ten-year period.Some of the reports coming out of these studies included NUREG/CR 5608,“Irradiation-Assisted Stress Corrosion Cracking of Model AusteniticStainless Steels Irradiated in the Halden Reactor”; NUREG/CR-6892,“Fracture Toughness and Crack Growth Rates of Irradiated AusteniticStainless Steels”; NUREG/CR-6687, “Irradiation-Assisted Stress CorrosionCracking of Model Austenitic Stainless Steel Alloys”; NUREG/CR-6915,“Irradiation-Assisted Stress Corrosion Cracking of Austenitic StainlessSteels and Alloy 690 from Halden Phase-II Irradiations”; NUREG/CR-6960,“Crack Growth Rates and Fracture Toughness of Irradiated AusteniticStainless Steels in BWR Environments”; and NUREG/CR-7018,“Irradiation-Assisted Stress Corrosion Cracking of Austenitic StainlessSteels in BWR Environments”.

FIG. 1 is a sectional view, with parts cut away, of reactor pressurevessel (“RPV”) 100 in a related art BWR.

During operation of the BWR, coolant water circulating inside RPV 100may be heated by nuclear fission produced in core 102. Feedwater may beadmitted into RPV 100 via feedwater inlet 104 and feedwater sparger 106(a ring-shaped pipe that may include apertures for circumferentiallydistributing the feedwater inside RPV 100). The feedwater from feedwatersparger 106 may flow down through downcomer annulus 108 (an annularregion between RPV 100 and core shroud 110).

Core shroud 110 may be a stainless steel cylinder that surrounds core102. Core 102 may include a multiplicity of fuel bundle assemblies 112(two 2×2 arrays, for example, are shown in FIG. 1). Each array of fuelbundle assemblies 112 may be supported at or near its top by top guide114 and/or at or near its bottom by core plate 116. Top guide 114 mayprovide lateral support for the top of fuel bundle assemblies 112 and/ormay maintain correct fuel-channel spacing to permit control rodinsertion.

The feedwater/coolant water may flow downward through downcomer annulus108 and/or into core lower plenum 118. The coolant water in core lowerplenum 118 may in turn flow up through core 102. The coolant water mayenter fuel assemblies 112, wherein a boiling boundary layer may beestablished. A mixture of water and steam may exit core 102 and/or mayenter core upper plenum 120 under shroud head 122. Core upper plenum 120may provide standoff between the steam-water mixture exiting core 102and entering standpipes 124. Standpipes 124 may be disposed atop shroudhead 122 and/or in fluid communication with core upper plenum 120.

The steam-water mixture may flow through standpipes 124 and/or may entersteam separators 126 (which may be, for example, of the axial-flow,centrifugal type). Steam separators 126 may substantially separate thesteam-water mixture into liquid water and steam. The separated liquidwater may mix with feedwater in mixing plenum 128. This mixture then mayreturn to core 102 via downcomer annulus 108. The separated steam maypass through steam dryers 130 and/or may enter steam dome 132. The driedsteam may be withdrawn from RPV 100 via steam outlet 134 for use inturbines and other equipment (not shown).

The BWR also may include a coolant recirculation system that providesthe forced convection flow through core 102 necessary to attain therequired power density. A portion of the water may be sucked from thelower end of downcomer annulus 108 via recirculation water outlet 136and/or may be forced by a centrifugal recirculation pump (not shown)into a plurality of jet pump assemblies 138 (only one of which is shown)via recirculation water inlets 140. Jet pump assemblies 138 may becircumferentially distributed around core shroud 110 and/or may providethe required reactor core flow.

As shown in FIG. 1, a related art jet pump assembly 138 may include apair of inlet mixers 142. A related art BWR may include 16 to 24 inletmixers 142. Each inlet mixer 142 may have an elbow 144 welded to it thatreceives water from a recirculation pump (not shown) via inlet riser146. An example inlet mixer 142 may include a set of five nozzlescircumferentially distributed at equal angles about the axis of inletmixer 142. Each nozzle may be tapered radially inwardly at its outlet.Jet pump assembly 138 may be energized by these convergent nozzles. Fivesecondary inlet openings may be radially outside of the nozzle exits.Therefore, as jets of water exit the nozzles, water from downcomerannulus 108 may be drawn into inlet mixer 142 via the secondary inletopenings, where it may be mixed with coolant water from therecirculation pump. The coolant water then may flow into diffuser 148.

FIG. 2 is a schematic diagram showing a developed azimuthal view of theinterior of a related BWR core shroud that comprises a plurality ofshell sections, having vertical seam welds, that are welded together,one upon the next, by horizontal seam welds.

As shown in FIG. 2, core shroud 200 may comprise first shell sections202 a and 202 b, second shell sections 204 a and 204 b, third shellsections 206 a and 206 b, fourth shell sections 208 a and 208 b, andfifth shell sections 210 a, 210 b, and 210 c. Core shroud 200 may besupported by shroud supports 212 a, 212 b, and 212 c, as well as shroudsupport plate 214.

Shroud supports 212 a, 212 b, and 212 c may be joined together usingvertical seam welds V12, V13, and V14, and also may be joined usinghorizontal seam weld H8 to shroud support plate 214.

Fifth shell sections 210 a, 210 b, and 210 c may be joined togetherusing vertical seam welds V9, V10, and V11 to form a lower shell sectionof core shroud 200, and also may be joined using horizontal seam weld H7to shroud supports 212 a, 212 b, and 212 c.

Fourth shell sections 208 a and 208 b may be joined together usingvertical seam welds V7 and V8 to form a bottom mid-core shell section ofcore shroud 200, and also may be joined using horizontal seam welds H6Aand H6B to fifth shell sections 210 a, 210 b, and 210 c. Horizontal seamweld H6A may represent the joining of fourth shell sections 208 a and208 b to core plate support ring 216; horizontal seam weld H6B mayrepresent the joining of core plate support ring 216 to fifth shellsections 210 a, 210 b, and 210 c.

Third shell sections 206 a and 206 b may be joined together usingvertical seam welds V5 and V6 to form a middle mid-core shell section ofcore shroud 200, and also may be joined using horizontal seam weld H5 tofourth shell sections 208 a and 208 b.

Second shell sections 204 a and 204 b may be joined together usingvertical seam welds V3 and V4 to form a top mid-core shell section ofcore shroud 200, and also may be joined using horizontal seam weld H4 tothird shell sections 206 a and 206 b.

First shell sections 202 a and 202 b may be joined together usingvertical seam welds V1 and V2 to form an upper shell section of coreshroud 200, and also may be joined using horizontal seam welds H2 and H3to second shell sections 204 a and 204 b. Horizontal seam weld H2 mayrepresent the joining of first shell sections 202 a and 202 b to topguide support ring 218; horizontal seam weld H3 may represent thejoining of top guide support ring 218 to second shell sections 204 a and204 b.

Horizontal seam weld H1 may represent the joining of shroud flange 220to first shell sections 202 a and 202 b.

As known to a PHOSITA, the relative offsets in vertical seam weldsV1-V14 attempt to ensure that a crack in a single vertical seam weldcannot propagate over a significant distance (e.g., all the way fromhorizontal seam weld H1 to horizontal seam weld H8). However, horizontalseam weld H1-H8 do not have such an offset arrangement.

Although SCC, IGSCC, and IASCC have been studied, no “cure” has beenfound. As a result, cracks continue to initiate and propagate incomponents of nuclear reactors. Core shrouds may be particularlysusceptible due to their extremely high neutron fluence as the nuclearreactor ages. For example, in core shroud 200, the active fuel in anassociated core 102 may extend vertically from between horizontal seamwelds H5 and H6A to about horizontal seam weld H2 or H3. Thus,horizontal seam welds H2, H3, H4, and H5, and vertical seam welds V3,V4, V5, V6, V7, and V8, all may be described as being subject toextremely high neutron fluence. In the event of SCC, IGSCC, or IASCC ofthe seam welds, core shroud 200 could be replaced. However, a moreeconomically feasible approach might be to conduct weld repair or tostructurally replace the horizontal seam welds, vertical seams welds, orboth.

Such a weld repair may be done with the seam welds submerged, but thisapproach may be difficult from a technical point of view. Such a weldrepair also may be done with the seam welds not submerged, but thisapproach may present other issues, such as significant radiationexposure and extension of the critical path during an outage.

As known to a PHOSITA, tie-rods have been proposed to structurallyreplace the horizontal seam welds as a group. Although tie-rods mayprovide significant support for the horizontal seam welds as a group,such tie-rods may not be as effective in structurally replace individualhorizontal seam welds.

As also known to a PHOSITA, various devices have been proposed tostructurally replace the vertical seam welds. Most of these devicesinvolved full penetration of the structure that includes the verticalseam welds. Although such devices may be employed, full penetration ofthe structure that includes the vertical seam welds may introduce otherproblems, such as creating potential leakage paths, complicatinginstallation procedures and reactor safety calculations, andestablishing new periodic inspection requirements.

Thus, a need exists for apparatuses and methods that may provide theability to structurally replace individual welds in nuclear reactorcomponents subject to SCC, IGSCC, or IASCC. In the case of core shroud200, this may include structurally replacing individual horizontal seamwelds, individual vertical seams welds, or both. In particular, a needexists for apparatuses and methods that may provide the ability tostructurally replace individual welds in nuclear reactor componentssubject to SCC, IGSCC, or IASCC without fully penetrating a structurethat includes the individual welds.

Related art systems, methods, and/or filters for apparatuses and methodsfor structurally replacing cracked welds are discussed, for example, inU.S. Pat. No. 5,392,322 to Whitling et al. (“the '322 patent”); U.S.Pat. No. 5,521,951 to Charnley et al. (“the '951 patent”); U.S. Pat. No.5,530,219 to Offer et al. (“the '219 patent”); U.S. Pat. No. 5,538,381to Erbes (“the '381 patent”); U.S. Pat. No. 5,621,778 to Erbes (“the'778 patent”); U.S. Pat. No. 5,675,619 to Erbes et al. (“the '619patent”); U.S. Pat. No. 5,712,887 to Thompson et al. (“the '887patent”); U.S. Pat. No. 5,729,581 to Loock et al. (“Loock”); U.S. Pat.No. 5,737,379 to Erbes (“the '379 patent”); U.S. Pat. No. 5,742,653 toErbes et al. (“the '653 patent”); U.S. Pat. No. 5,802,129 to Deaver etal. (“the '129 patent”); U.S. Pat. No. 5,803,686 to Erbes et al. (“the'686 patent”); U.S. Pat. No. 5,803,688 to Gleason et al. (“the '688patent”); U.S. Pat. No. 6,067,338 to Erbes (“the '338 patent”); U.S.Pat. No. 6,138,353 to Weems et al. (“Weems I”); U.S. Pat. No. 6,343,107B1 to Erbes et al. (“the '107 patent”); U.S. Pat. No. 6,345,927 B1 toPao et al. (“the '927 patent”); U.S. Pat. No. 6,371,685 B1 to Weems etal. (“Weems II”); U.S. Pat. No. 6,464,424 B1 to Weems et al. (“WeemsIII”); and U.S. Pat. No. 7,649,970 B2 to Erbes (“the '970 patent”); andin U.S. Patent Publication No. 2003/0234541 A1 to Thompson et al. (“the'541 publication”); U.S. Patent Publication No. 2011/0101177 A1 toSuganuma et al. (“Suganuma I”); and U.S. Patent Publication No.2012/0087456 A1 to Suganuma et al. (“Suganuma II”).

The disclosures of the '107 patent, the '129 patent, the '219 patent,the '322 patent, the '338 patent, the '379 patent, the '381 patent, the'619 patent, the '653 patent, the '686 patent, the '688 patent, the '778patent, the '887 patent, the '927 patent, the '951 patent, and the '970patent are incorporated in this application by reference in theirentirety. Similarly, the disclosures of the '541 publication areincorporated in this application by reference in its entirety.

SUMMARY

Example embodiments may provide apparatuses and methods for structurallyreplacing cracked welds. Example embodiments may provide apparatuses andmethods for structurally replacing cracked welds of nuclear plants.

In some example embodiments, an apparatus configured to structurallyreplace a cracked weld in a nuclear plant may comprise: a first bodyportion that comprises a first gripping portion; a second body portionthat comprises a second gripping portion; a wedge portion between thefirst and second body portions; and/or an adjustment portion. The firstbody portion may be configured to slidably engage the second bodyportion. The wedge portion may be configured to exert force on theslidably engaged first and second body portions. The adjustment portionmay be configured to increase or decrease the force exerted by the wedgeportion on the slidably engaged first and second body portions. When theadjustment portion increases the force exerted by the wedge portion onthe slidably engaged first and second body portions, a distance betweenthe first and second gripping portions may decrease.

In some example embodiments, the adjustment portion may be furtherconfigured to prevent the distance between the first and second grippingportions from increasing.

In some example embodiments, the apparatus may further comprise aretaining portion. The retaining portion may be configured to interactwith the adjustment portion so as to prevent the distance between thefirst and second gripping portions from increasing.

In some example embodiments, an apparatus configured to structurallyreplace a cracked weld in a nuclear plant may comprise: a body thatcomprises a first end, a second end, and a portion between the first andsecond ends. The first end may comprise a first gripping portion. Thesecond end may comprise a second gripping portion. When the body is inan unflexed state, the first gripping portion and the second grippingportion may be a first distance apart. When the body is in a flexedstate, the first gripping portion and the second gripping portion may bea second distance apart. The second distance may be greater than thefirst distance.

In some example embodiments, when the body is in the unflexed state, thebody may have a first shape. When the body is in the flexed state, thebody has a second shape. The first shape may be more curved than thesecond shape.

In some example embodiments, when the body is in the flexed state, thefirst gripping portion may be configured to enter a first slot on afirst side of the cracked weld in a structure that includes the crackedweld and the second gripping portion may be configured to enter a secondslot on a second side of the cracked weld in the structure that includesthe cracked weld. When the body is in the unflexed state, the firstgripping portion may be configured to grip the first slot on the firstside of the cracked weld in the structure that includes the cracked weldand the second gripping portion may be configured to grip the secondslot on the second side of the cracked weld in the structure thatincludes the cracked weld.

In some example embodiments, an apparatus configured to structurallyreplace a cracked weld in a nuclear plant may comprise: a first bodyportion that comprises a first gripping portion; a second body portionthat comprises a second gripping portion; and/or an adjustment portion.The first body portion may be configured to slidably engage the secondbody portion. The adjustment portion may be configured to exert force onthe slidably engaged first and second body portions. The adjustmentportion may be further configured to increase or decrease the forceexerted on the slidably engaged first and second body portions. When theadjustment portion increases the force exerted on the slidably engagedfirst and second body portions, a distance between the first and secondgripping portions may decrease.

In some example embodiments, the adjustment portion may be furtherconfigured to prevent the distance between the first and second grippingportions from increasing.

In some example embodiments, the apparatus may further comprise aretaining portion. The retaining portion may be configured to interactwith the adjustment portion so as to prevent the distance between thefirst and second gripping portions from increasing.

In some example embodiments, a method for structurally replacing acracked weld in a nuclear plant may comprise: obtaining an apparatusthat comprises a first body portion comprising a first gripping portion,a second body portion comprising a second gripping portion, a wedgeportion between the first and second body portions, and an adjustmentportion, wherein the first body portion is configured to slidably engagethe second body portion, wherein the wedge portion is configured toexert a first force on the slidably engaged first and second bodyportions, wherein the adjustment portion is configured to increase ordecrease the first force exerted by the wedge portion on the slidablyengaged first and second body portions, and wherein when the adjustmentportion increases the first force exerted by the wedge portion on theslidably engaged first and second body portions, a distance between thefirst and second gripping portions decreases; forming slots on bothsides of the cracked weld in a structure that includes the cracked weld,wherein the slots do not fully penetrate the structure; disposing theapparatus near a surface of the structure so that the first grippingportion is in a first slot on a first side of the cracked weld and thesecond gripping portion is in a second slot on a second side of thecracked weld; and/or using the adjustment portion to increase the firstforce exerted by the wedge portion on the slidably engaged first andsecond body portions so as to decrease the distance between the firstand second gripping portions until the first gripping portion grips thefirst slot and the second gripping portion grips the second slot with asecond force that structurally replaces the cracked weld.

In some example embodiments, the method may not comprise removingmaterial from the cracked weld.

In some example embodiments, the method may not comprise removingmaterial from a weld heat-affected zone around the cracked weld.

In some example embodiments, the slots may be formed outside of a weldheat-affected zone around the cracked weld.

In some example embodiments, a method for structurally replacing acracked weld in a nuclear plant may comprise: forming slots on bothsides of the cracked weld in a structure that includes the cracked weld,wherein the slots do not fully penetrate the structure; disposing a bodynear a surface of the structure, the body comprising a first end, asecond end, and a portion between the first and second ends, wherein thefirst end comprises a first gripping portion, and wherein the second endcomprises a second gripping portion; changing the body from an unflexedstate in which the first gripping portion and the second grippingportion are a first distance apart to a flexed state in which the firstgripping portion and the second gripping portion are a second distanceapart, wherein the second distance is greater than the first distance;moving the body in the flexed state so that the first gripping portionis in a first slot on a first side of the cracked weld and the secondgripping portion is in a second slot on a second side of the crackedweld; and/or changing the body from the flexed state to the unflexedstate so that the first gripping portion grips the first slot and thesecond gripping portion grips the second slot with a force thatstructurally replaces the cracked weld.

In some example embodiments, the method may not comprise removingmaterial from the cracked weld.

In some example embodiments, the method may not comprise removingmaterial from a weld heat-affected zone around the cracked weld.

In some example embodiments, the slots may be formed outside of a weldheat-affected zone around the cracked weld.

In some example embodiments, a method for structurally replacing acracked weld in a nuclear plant may comprise: obtaining an apparatusthat comprises a first body portion comprising a first gripping portion,a second body portion comprising a second gripping portion, and anadjustment portion, wherein the first body portion is configured toslidably engage the second body portion, wherein the adjustment portionis configured to exert a first force on the slidably engaged first andsecond body portions, wherein the adjustment portion is furtherconfigured to increase or decrease the first force exerted on theslidably engaged first and second body portions, and wherein when theadjustment portion increases the first force exerted on the slidablyengaged first and second body portions, a distance between the first andsecond gripping portions decreases; forming slots on both sides of thecracked weld in a structure that includes the cracked weld, wherein theslots do not fully penetrate the structure; disposing the apparatus neara surface of the structure so that the first gripping portion is in afirst slot on a first side of the cracked weld and the second grippingportion is in a second slot on a second side of the cracked weld; and/orusing the adjustment portion to increase the first force exerted on theslidably engaged first and second body portions so as to decrease thedistance between the first and second gripping portions until the firstgripping portion grips the first slot and the second gripping portiongrips the second slot with a second force that structurally replaces thecracked weld.

In some example embodiments, the method may not comprise removingmaterial from the cracked weld.

In some example embodiments, the method may not comprise removingmaterial from a weld heat-affected zone around the cracked weld.

In some example embodiments, the slots may be formed outside of a weldheat-affected zone around the cracked weld.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects and advantages will become more apparentand more readily appreciated from the following detailed description ofexample embodiments, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a sectional view, with parts cut away, of an RPV in a relatedart BWR;

FIG. 2 is a schematic diagram showing a developed azimuthal view of theinterior of a related BWR core shroud that comprises a plurality ofshell sections, having vertical seam welds, that are welded together,one upon the next, by horizontal seam welds;

FIG. 3A is a diagram of a core shroud prior to preparation of outersurfaces of the core shroud near a weld according to some exampleembodiments;

FIG. 3B is a diagram of a core shroud after preparation of outersurfaces of the core shroud near a weld according to some exampleembodiments;

FIG. 3C is a perspective view of a core shroud, outer surfaces, a weld,and slots according to some example embodiments;

FIG. 3D is a top view of a core shroud, outer surfaces, a weld, andslots according to some example embodiments;

FIG. 4A is a front-side perspective view of an apparatus configured tostructurally replace a cracked weld in a nuclear plant according to someexample embodiments;

FIG. 4B is a back-side perspective view of an apparatus configured tostructurally replace a cracked weld in a nuclear plant according to someexample embodiments;

FIG. 4C is a top view of a body in an unflexed state and in a flexedstate according to some example embodiments;

FIG. 4D is a front-side perspective view of a tool configured to assistan operator in changing a body from an unflexed state to a flexed stateor from the flexed state to the unflexed state according to some exampleembodiments;

FIG. 4E is a front-side perspective view of a tool mated with anapparatus configured to structurally replace a cracked weld in a nuclearplant according to some example embodiments;

FIG. 4F is a back-side perspective view of a tool mated with anapparatus configured to structurally replace a cracked weld in a nuclearplant, a first gripping portion in a first slot, and a second grippingportion in a second slot according to some example embodiments;

FIG. 4G is a back-side perspective view of an apparatus configured tostructurally replace a cracked weld in a nuclear plant, after withdrawala tool configured to assist an operator in changing a body from anunflexed state to a flexed state or from the flexed state to theunflexed state, according to some example embodiments;

FIG. 4H is a front view of two apparatuses configured to structurallyreplace a cracked weld in a nuclear plant, at vertical seam weld V3 orV4 according to some example embodiments;

FIG. 4I is a front view of three apparatuses configured to structurallyreplace a cracked weld in a nuclear plant, at vertical seam weld V5 orV6 according to some example embodiments;

FIG. 5A is a front-side, exploded, perspective view of an apparatusconfigured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments;

FIG. 5B is an outline view of the apparatus of FIG. 5A;

FIG. 5C is a front perspective view of an assembled apparatus configuredto structurally replace a cracked weld in a nuclear plant according tosome example embodiments;

FIG. 5D is another front perspective view of the assembled apparatus ofFIG. 5C;

FIG. 5E is a top view of the assembled apparatus of FIG. 5C;

FIG. 5F is a back perspective view of the assembled apparatus of FIG.5C;

FIG. 5G is a front perspective outline view of an assembled apparatusconfigured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments;

FIG. 5H is a top view of the assembled apparatus of FIG. 5G, with afirst gripping portion in a first slot and a second gripping portion ina second slot;

FIG. 5I is a cross-sectional view of an assembled apparatus configuredto structurally replace a cracked weld in a nuclear plant, taken along acenterline of the apparatus, with a first gripping portion in a firstslot and a second gripping portion in a second slot, according to someexample embodiments;

FIG. 5J is another cross-sectional view of the assembled apparatus FIG.5I taken along a centerline of the apparatus;

FIG. 5K is a front view of three apparatuses, configured to structurallyreplace a cracked weld in a nuclear plant, at a vertical seam weldaccording to some example embodiments;

FIG. 5L is an outline view of the three apparatuses of FIG. 5K;

FIG. 5M is a front view of two apparatuses, configured to structurallyreplace a cracked weld in a nuclear plant, at a vertical seam weldaccording to some example embodiments;

FIG. 5N is a view looking up at the two apparatuses of FIG. 5M;

FIG. 5O is a view looking up at the three apparatuses of FIG. 5K;

FIG. 6A is a front-side, exploded, perspective view of an apparatusconfigured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments;

FIG. 6B is an enlarged perspective view of a wedge portion of FIG. 6A;

FIG. 6C is an enlarged perspective view of an adjustment portion of FIG.6A;

FIG. 6D is an enlarged perspective view of a retaining portion of FIG.6A;

FIG. 6E is an enlarged perspective view of a second body portion of FIG.6A;

FIG. 6F is an enlarged perspective view of a first body portion of FIG.6A;

FIG. 6G is a front perspective view of an assembled apparatus configuredto structurally replace a cracked weld in a nuclear plant according tosome example embodiments;

FIG. 6H is a back perspective view of the assembled apparatus of FIG.6G;

FIG. 6I is a front perspective view of the assembled apparatus of FIG.6G, with a first gripping portion in a first slot and a second grippingportion in a second slot;

FIG. 6J is a front perspective outline view of the assembled apparatusof FIG. 6I;

FIG. 6K is a top view of the assembled apparatus of FIG. 6I;

FIG. 6L is a bottom outline view of the assembled apparatus of FIG. 6I;

FIG. 7 is a flow chart illustrating a first method for structurallyreplacing a cracked weld in a nuclear plant according to some exampleembodiments;

FIG. 8 is a flow chart illustrating a second method for structurallyreplacing a cracked weld in a nuclear plant according to some exampleembodiments; and

FIG. 9 is a flow chart illustrating a third method for structurallyreplacing a cracked weld in a nuclear plant according to some exampleembodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments will now be described more fully with reference tothe accompanying drawings. Embodiments, however, may be embodied in manydifferent forms and should not be construed as being limited to theembodiments set forth herein. Rather, these example embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope to those skilled in the art. In the drawings, thethicknesses of layers and regions are exaggerated for clarity.

It will be understood that when an element is referred to as being “on,”“connected to,” “electrically connected to,” or “coupled to” to anothercomponent, it may be directly on, connected to, electrically connectedto, or coupled to the other component or intervening components may bepresent. In contrast, when a component is referred to as being “directlyon,” “directly connected to,” “directly electrically connected to,” or“directly coupled to” another component, there are no interveningcomponents present. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers, and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, and/or section from another element, component, region, layer,and/or section. For example, a first element, component, region, layer,and/or section could be termed a second element, component, region,layer, and/or section without departing from the teachings of exampleembodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper,” and the like may be used herein for ease of description todescribe the relationship of one component and/or feature to anothercomponent and/or feature, or other component(s) and/or feature(s), asillustrated in the drawings. It will be understood that the spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures.

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes,” and/or “including,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andshould not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

The term “irradiation relaxation” means stress relaxation ofcorresponding metals due to exposure to ionizing radiation, particularlyneutron fluence in a nuclear plant.

The term “structurally replace” means to assume all mechanical loads forwhich the original load-bearing member was responsible.

The term “thermal tightening” means that a first body with a firstcoefficient of thermal expansion is outside of a second body with asecond coefficient of thermal expansion, where the second coefficient ofthermal expansion is higher. When the first and second bodies areheated, the second body expands more than the first body, causing thefirst body to constrain its movement, but from the frame of reference ofthe second body, the first body has tightened on the second body.

The term “weld heat-affected zone” means an area of metal that has hadits microstructure and properties altered by welding.

Reference will now be made to example embodiments, which are illustratedin the accompanying drawings, wherein like reference numerals may referto like components throughout.

FIG. 3A is a diagram of core shroud 300 prior to preparation of outersurfaces 302 a and 302 b of core shroud 300 near weld 302 c according tosome example embodiments. FIG. 3B is a diagram of core shroud 300 afterpreparation of outer surfaces 302 a and 302 b of core shroud 300 nearweld 302 c according to some example embodiments.

FIG. 3A shows jet pump assembly 304, including inlet riser 306, riserbrace 308, left-hand transition piece 310, left-hand secondary inletopenings 312, and left-hand inlet mixer 314. The correspondingright-hand transition piece, right-hand secondary inlet openings, andright-hand inlet mixer of jet pump assembly 304 may be removed tofacilitate access to outer surfaces 302 a and 302 b of core shroud 300near weld 302 c. Although tie-rods associated with core shroud 300 maybe removed to facilitate access to outer surface 302 a of core shroud300 near weld 302 c, the apparatuses and methods of the presentapplication may allow the tie-rods to remain in place. FIG. 3A alsoshows jet pump assembly 316, including inlet riser 318, riser brace 320,right-hand transition piece 322, right-hand secondary inlet openings324, and right-hand inlet mixer 326. The corresponding left-handtransition piece, left-hand secondary inlet openings, and left-handinlet mixer of jet pump assembly 304 may be removed to facilitate accessto outer surfaces 302 a and 302 b of core shroud 300 near weld 302 c.Although tie-rods associated with core shroud 300 may be removed tofacilitate access to outer surface 302 b of core shroud 300 near weld302 c, the apparatuses and methods of the present application may allowthe tie-rods to remain in place.

Similar to FIG. 3A, FIG. 3B shows jet pump assembly 304, including inletriser 306, riser brace 308, left-hand transition piece 310, left-handsecondary inlet openings 312, and left-hand inlet mixer 314. Thecorresponding right-hand transition piece, right-hand secondary inletopenings, and right-hand inlet mixer of jet pump assembly 304 may beremoved to facilitate access to outer surfaces 302 a and 302 b of coreshroud 300 near weld 302 c. Although tie-rods associated with coreshroud 300 may be removed to facilitate access to outer surface 302 a ofcore shroud 300 near weld 302 c, the apparatuses and methods of thepresent application may allow the tie-rods to remain in place. Similarto FIG. 3A, FIG. 3B also shows jet pump assembly 316, including inletriser 318, riser brace 320, right-hand transition piece 322, right-handsecondary inlet openings 324, and right-hand inlet mixer 326. Thecorresponding left-hand transition piece, left-hand secondary inletopenings, and left-hand inlet mixer of jet pump assembly 304 may beremoved to facilitate access to outer surfaces 302 a and 302 b of coreshroud 300 near weld 302 c. Although tie-rods associated with coreshroud 300 may be removed to facilitate access to outer surface 302 b ofcore shroud 300 near weld 302 c, the apparatuses and methods of thepresent application may allow the tie-rods to remain in place.

In addition, FIG. 3B shows an example of preparation work on outersurfaces 302 a and 302 b of core shroud 300 near weld 302 c. One or moreslots 328 may be formed in outer surface 302 a of core shroud 300 nearweld 302 c. Similarly, one or more slots 330 may be formed in outersurface 302 b of core shroud 300 near weld 302 c.

FIG. 3C is a perspective view of core shroud 300, outer surfaces 302 aand 302 b, weld 302 c, a slot 328, and a slot 330 according to someexample embodiments. FIG. 3D is a top view of core shroud 300, outersurfaces 302 a and 302 b, weld 302 c, a slot 328, and a slot 330according to some example embodiments.

As shown in FIGS. 3C and 3D, one or more slots 328 and one or more slots330 may not fully penetrate the structure core shroud 300 in order toavoid the potentially negative effects associated with such fullpenetrations. A thickness of core shroud 300 may be, for example,between about 1.5 inches and about 2.0 inches. A depth of one or moreslots 328 and one or more slots 330 may be, for example, up to 90% ofthe thickness of core shroud 300. The depth of one or more slots 328 andone or more slots 330 may be, for example, greater than or equal to 50%of the thickness of core shroud 300 and less than or equal to 70% of thethickness of core shroud 300.

One or more slots 328 and one or more slots 330 may be formed usingtechniques known to a PHOSITA, such as Electrical Discharge Machining(“EDM”). In some example embodiments, performance of the apparatuses andmethods of the present application may be improved by improving thequality and precision (e.g., positional accuracy and proper orientation)of such forming techniques.

As shown in FIGS. 3B-3D, each slot 328 may correspond to a slot 330, andeach slot 330 may correspond to a slot 328. Although not limited to aspecific shape, a volume associated with one or more slots 328 mayapproximate that of a rectangular solid. Similarly, although notconfined to a specific shape, a volume associated with one or more slots330 may approximate that of a rectangular solid. A size of therectangular solid might be, for example, about 3 inches wide, about 7inches tall, and about 1 inch deep. Because of scalability, however, oneor more of these dimensions could be bigger or smaller than thosevalues. Additionally, as discussed above, one or more slots 328 and oneor more slots 330 are not limited to a specific shape.

An edge of one or more slots 328 closer to weld 302 c may besubstantially parallel to weld 302 c. Similarly, an edge of one or moreslots 330 closer to weld 302 c may be substantially parallel to weld 302c.

An edge of one or more slots 328 closer to weld 302 c may besubstantially parallel to an edge of one or more slots 330 closer toweld 302 c. One or more slots 328 may be substantially parallel to oneor more slots 330. A distance from weld 302 c to one or more slots 328or one or more slots 330 may be, for example, greater than or equal toabout 3 inches and less than or equal to about 5 inches.

An edge of one or more slots 328 closer to weld 302 c may besubstantially perpendicular to outer surface 302 a. An edge of one ormore slots 328 closer to weld 302 c may be undercut so that at least oneportion of one or more slots 328 not at outer surface 302 a is closer toweld 302 c than the edge of one or more slots 328 at outer surface 302a. In some example embodiments, performance of the apparatuses andmethods of the present application may be improved by such undercuts.

One or more slots 328 may lie at an angle relative to one or more slots330 (e.g., forming a dovetail relationship). The angle may be, forexample, greater than or equal to about 5° and less than or equal toabout 20°. The angle may be, for example, about 10°. This angularrelationship may result from EDM techniques. This angular relationshipalso may result, for example, from curvature of outer surfaces 302 a and302 b of core shroud 300 near weld 302 c. Additionally, this angularrelationship may result, for example, from a radial orientation of EDMrelative to a curved or cylindrical surface. In some exampleembodiments, performance of the apparatuses and methods of the presentapplication may be improved this angular relationship.

FIG. 4A is a front-side perspective view of apparatus 400 configured tostructurally replace a cracked weld in a nuclear plant according to someexample embodiments; FIG. 4B is a back-side perspective view ofapparatus 400 according to some example embodiments.

Apparatus 400 may comprise body 402. Body 402 may be configured to actas a spring clamp.

Body 402 may comprise metal. The metal may have a coefficient of thermalexpansion that is less than a coefficient of thermal expansionassociated with the material of core shroud 300. Thus, when the nuclearplant is heated up, for example, to normal operating temperature, thisdifference in coefficients of thermal expansion may result in thermaltightening of body 402 with respect to core shroud 300. The metal maybe, for example, XM-19 stainless steel, a 600-series Inconel (e.g., 600,617, 625, or 690), a 700-series Inconel (e.g., 718 or X-750), orequivalent.

Body 402 may comprise first end 404, second end 406, and portion 408between first end 404 and second end 406. First end 404 may comprisefirst gripping portion 410. Second end 406 may comprise second grippingportion 412. Portion 408 may comprise section 414 configured to assistan operator in changing body 402 from an unflexed state to a flexedstate or from a flexed state to an unflexed state.

Body 402 may further comprise access 416 configured to allow a tool (notshown) to engage body 402 in order to assist an operator in changingbody 402 from an unflexed state to a flexed state or from a flexed stateto an unflexed state.

FIG. 4C is a top view of body 402 in unflexed state 418 and in flexedstate 420 according to some example embodiments. When body 402 is inunflexed state 418, first gripping portion 410 and second grippingportion 412 may be a first distance d1 apart. When body 402 is in flexedstate 420, first gripping portion 410 and second gripping portion 412may be a second distance d2 apart. Second distance d2 may be greaterthan first distance d1.

When body 402 is in unflexed state 418, body 402 may have a first shape.When body 402 is in flexed state 420, body 402 may have a second shape.The first shape may be more curved than the second shape.

When body 402 is in flexed state 420, first gripping portion 410 may beconfigured to enter slot 328 formed in outer surface 302 a of coreshroud 300 near weld 302 c (e.g., a cracked weld) and second grippingportion 412 may be configured to enter slot 330 formed in outer surface302 b of core shroud 300 near weld 302 c. When body 402 is in unflexedstate 418, first gripping portion 410 may be configured to grip slot 328and second gripping portion 412 may be configured to grip slot 330,compressing weld 302 c.

FIG. 4D is a front-side perspective view of tool 422 configured toassist an operator in changing body 402 from unflexed state 418 toflexed state 420 or from flexed state 420 to an unflexed state 418according to some example embodiments; FIG. 4E is a front-sideperspective view of tool 422 mated with apparatus 400 according to someexample embodiments; FIG. 4F is a back-side perspective view of tool 422mated with apparatus 400, first gripping portion 410 in slot 328, andsecond gripping portion 412 in slot 330 according to some exampleembodiments (in FIG. 4F, section 414 may or may not be in contact withweld 302 c); and FIG. 4G is a back-side perspective view of apparatus400, first gripping portion 410 in slot 328, and second gripping portion412 in slot 330, after withdrawal of tool 422, according to some exampleembodiments (in FIG. 4G, section 414 may or may not be in contact withweld 302 c).

Tool 422 may include main body 424, actuator 426, first arm 428, andsecond arm 430. Tool 422 may be configured to mate with apparatus 400using access 416. Actuator 426 (e.g., a hydraulic actuator using, forexample, demineralized water) may use first arm 428 to engage first end404 and second arm 430 to engage second end 406. Application ofhydraulic power to actuator 426 may then cause first arm 428 and secondarm 430 to change body 402 from unflexed state 418 to flexed state 420.Pressing of section 414 against core shroud 300 may increase mechanicaladvantage available in changing body 402 from unflexed state 418 toflexed state 420.

As would be understood by a PHOSITA, tool 422 may be remotely operatedby industry-standard equipment (e.g., attached to a handling pole usedby an operator from a servicing platform). As also would be understoodby a PHOSITA, tool 422 may be hydraulically powered by industry-standardequipment. Additionally, as would be understood by a PHOSITA, tool 422should not flex apparatus 400 beyond the yield strength of the materialof apparatus 400.

FIG. 4H is a front view of two apparatuses 400, configured tostructurally replace a cracked weld in a nuclear plant, at vertical seamweld V3 or V4 according to some example embodiments; FIG. 4I is a frontview of three apparatuses 400, configured to structurally replace acracked weld in a nuclear plant, at vertical seam weld V5 or V6according to some example embodiments.

According to some example embodiments, apparatuses 400 may be scalablein size and the amount of force applied. Thus, there may be trade-offsbetween the size of the apparatuses 400 used and the number ofapparatuses 400 used (e.g., fewer bigger apparatuses 400 versus morenumerous smaller apparatuses 400). As would be understood by a PHOSITA,many factors may play into such a decision, such as length of outage,critical path considerations, physical limitations on access to weld 302c, etc.

According to some example embodiments, apparatuses 400 may be easilyinstalled, removed, replaced, or inspected. According to some exampleembodiments, apparatuses 400 may be of single-piece construction.

According to some example embodiments, apparatuses 400 may be pre-loadedso as to prevent damage due to vibration, taking into considerationfactors such as irradiation relaxation and thermal tightening. Accordingto some example embodiments, apparatuses 400 may be pre-loaded toaccount for hoop stresses, such as normal, upset, and loss of coolantaccident (“LOCA”) hoop stresses. According to some example embodiments,apparatuses 400 may be pre-loaded to account for pressure differencesacross core shroud 300, such as normal, upset, and LOCA differentialpressures.

FIG. 5A is a front-side, exploded, perspective view of apparatus 500configured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments; FIG. 5B is an outline view ofapparatus 500 of FIG. 5A.

Apparatus 500 may comprise first body portion 502, second body portion504, and adjustment portion 506. Apparatus 500 may be pre-assembledprior to installation (e.g., on the refueling floor), simplifying thatprocess. Apparatus 500 may be configured to act as a self-aligningclamp.

First body portion 502 may comprise first gripping portion 508. Secondbody portion 504 may comprise second gripping portion 510. First bodyportion 502 may be configured to slidably engage second body portion504.

Adjustment portion 506 may be configured to exert force on the slidablyengaged first body portion 502 and second body portion 504. Adjustmentportion 506 may be further configured to increase or decrease the forceexerted on force on the slidably engaged first body portion 502 andsecond body portion 504. When adjustment portion 506 increases the forceexerted on force on the slidably engaged first body portion 502 andsecond body portion 504, a distance between first gripping portion 508and second gripping portion 510 may decrease, compressing weld 302 c(assuming that apparatus 500 is in use to structurally replace a crackedweld).

First gripping portion 508 may be configured to enter slot 328 formed inouter surface 302 a of core shroud 300 near weld 302 c (e.g., a crackedweld) and second gripping portion 510 may be configured to enter slot330 formed in outer surface 302 b of core shroud 300 near weld 302 c.When adjustment portion 506 exerts force on the slidably engaged firstbody portion 502 and second body portion 504, first gripping portion 508may be configured to grip slot 328 and second gripping portion 510 maybe configured to grip slot 330, compressing weld 302 c.

Adjustment portion 506 may be further configured to prevent the distancebetween first body portion 502 and second body portion 504 fromincreasing. Such a retention feature may include, for example, a detentmechanism, locking tab, pin, or ratchet mechanism.

Adjustment portion 506 may comprise stud 512 and nut 514. Stud 512 maycomprise first end 516 and second end 518. First end 516 of stud 512 maybe configured to fit into access 520 in first body portion 502. Firstend 516 of stud 512 may be further configured to interact with nut 514.For example, stud 512 may be threaded near first end 516 so as to matewith nut 514. Tightening nut 514 may draw first end 516 through nut 514,moving first gripping portion 508 and second gripping portion 510 closertogether or, if first gripping portion 508 is already gripping slot 328and second gripping portion 510 is already gripping slot 330,compressing weld 302 c.

Access 520 may be configured to interact with nut 514 so as to allow theslidable engagement of first body portion 502 and second body portion504 when first body portion 502 and second body portion 504 are notdirectly in line with one another. This self-aligning feature mayinclude, for example, a ball and seat arrangement in which access 520may provide a substantially spherical seat and nut 514 may provide acorresponding substantially spherical ball. This self-aligning featuremay reduce dependency on the quality and precision of the formingtechniques for one or more slots 328 and one or more slots 330.

Second end 518 of stud 512 may be configured to fit into access 522 insecond body portion 504. When first body portion 502 and second bodyportion 504 are slidably engaged, second end 518 of stud 512 mayinteract with access 522 so as to prevent rotation of stud 512 relativeto second body portion 504.

Apparatus 500 may further comprise retaining portion 516. Retainingportion 516 may be configured to interact with nut 514 so as to preventthe distance between first body portion 502 and second body portion 504from increasing. Such a retention feature may include, for example, adetent mechanism, locking tab, pin, or ratchet mechanism.

FIG. 5C is a front perspective view of assembled apparatus 500configured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments; FIG. 5D is another frontperspective view of assembled apparatus 500 of FIG. 5C; FIG. 5E is a topview of assembled apparatus 500 of FIG. 5C; and FIG. 5F is a backperspective view of assembled apparatus 500 of FIG. 5C.

FIG. 5G is a front perspective outline view of assembled apparatus 500configured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments; and FIG. 5H is a top view ofassembled apparatus 500 of FIG. 5G, with first gripping portion 508 inslot 328 and second gripping portion 510 in slot 330.

FIG. 5I is a cross-sectional view of assembled apparatus 500 configuredto structurally replace a cracked weld in a nuclear plant, taken along acenterline of apparatus 500, with first gripping portion 508 in slot 328and second gripping portion 510 in slot 330, according to some exampleembodiments; and FIG. 5J is another cross-sectional view of assembledapparatus 500 of FIG. 5I taken along a centerline of apparatus 500.

FIG. 5K is a front view of three apparatuses 500, configured tostructurally replace a cracked weld in a nuclear plant, at vertical seamweld V5 or V6 according to some example embodiments; and FIG. 5L is anoutline view of the three apparatuses 500 of FIG. 5K. A tie-rod 524 isvisible in both FIGS. 5K and 5L.

FIG. 5M is a front view of two apparatuses 500, configured tostructurally replace a cracked weld in a nuclear plant, at vertical seamweld V3 or V4 according to some example embodiments; FIG. 5N is a viewlooking up at the two apparatuses 500 of FIG. 5M; and FIG. 5O is a viewlooking up at the three apparatuses 500 of FIG. 5K.

As would be understood by a PHOSITA, apparatus 500 may be remotelyinstalled using industry-standard equipment (e.g., attached to ahandling pole used by an operator from a servicing platform andtightened using a remotely operated tool).

According to some example embodiments, apparatuses 500 may be scalablein size and the amount of force applied. Thus, there may be trade-offsbetween the size of the apparatuses 500 used and the number ofapparatuses 500 used (e.g., fewer bigger apparatuses 500 versus morenumerous smaller apparatuses 500). As would be understood by a PHOSITA,many factors may play into such a decision, such as length of outage,critical path considerations, physical limitations on access to weld 302c, etc.

According to some example embodiments, apparatuses 500 may be easilyinstalled, removed, replaced, or inspected. According to some exampleembodiments, apparatuses 500 may have a low profile (e.g., wheninstalled, not protruding from core shroud 300 by more than about 4inches) so as to improve accessibility to weld 302 c even if tie-rodsassociated with core shroud 300 are not removed.

According to some example embodiments, apparatuses 500 may be pre-loadedso as to prevent damage due to vibration, taking into considerationfactors such as irradiation relaxation and thermal tightening. Accordingto some example embodiments, apparatuses 500 may be pre-loaded toaccount for hoop stresses, such as normal, upset, and LOCA hoopstresses. According to some example embodiments, apparatuses 500 may bepre-loaded to account for pressure differences across core shroud 300,such as normal, upset, and LOCA differential pressures.

FIG. 6A is a front-side, exploded, perspective view of apparatus 600configured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments.

Apparatus 600 may comprise first body portion 602, second body portion604, wedge portion 606 between first body portion 602 and second bodyportion 604, and adjustment portion 608. Apparatus 600 may bepre-assembled prior to installation (e.g., on the refueling floor),simplifying that process. Apparatus 600 may be configured to act as awedge clamp.

First body portion 602 may comprise first gripping portion 610. Secondbody portion 604 may comprise second gripping portion 612. First bodyportion 602 may be configured to slidably engage second body portion604.

Wedge portion 606 may be configured to exert force on the slidablyengaged first body portion 602 and second body portion 604. Adjustmentportion 608 may be configured to increase or decrease the force exertedby wedge portion 606 on the slidably engaged first body portion 602 andsecond body portion 604. When adjustment portion 608 increases the forceexerted by wedge portion 606 on the slidably engaged first body portion602 and second body portion 604, a distance between first grippingportion 610 and second gripping portion 612 may decrease, compressingweld 302 c (assuming that apparatus 600 is in use to structurallyreplace a cracked weld).

Adjustment portion 608 may act near an end of wedge portion 606 (e.g.,wedge portion 606 may have a threaded end and adjustment portion 608 maybe a nut). Tightening the nut may draw wedge portion 606 through theslidably engaged first body portion 602 and second body portion 604,moving first gripping portion 610 and second gripping portion 612 closertogether or, if first gripping portion 610 is already gripping slot 328and second gripping portion 612 is already gripping slot 330,compressing weld 302 c.

Adjustment portion 608 may be further configured to prevent the distancebetween first gripping portion 610 and second gripping portion 612 fromincreasing.

Conveniently, adjustment portion 608 may be oriented vertically so as tosimply the process of mating an operating tool to adjustment portion 608(e.g., the operating tool may be attached to a handling pole used by anoperator from a servicing platform above adjustment portion 608).

Apparatus 600 may further comprise retaining portion 614. Retainingportion 614 may be configured to interact with adjustment portion 608 soas to prevent the distance between first gripping portion 610 and secondgripping portion 612 from increasing.

FIG. 6B is an enlarged perspective view of wedge portion 606 of FIG. 6A;FIG. 6C is an enlarged perspective view of adjustment portion 608 ofFIG. 6A; FIG. 6D is an enlarged perspective view of retaining portion614 of FIG. 6A; FIG. 6E is an enlarged perspective view of second bodyportion 604 of FIG. 6A; and FIG. 6F is an enlarged perspective view offirst body portion 602 of FIG. 6A.

FIG. 6G is a front perspective view of assembled apparatus 600configured to structurally replace a cracked weld in a nuclear plantaccording to some example embodiments; FIG. 6H is a back perspectiveview of assembled apparatus 600 of FIG. 6G; FIG. 6I is a frontperspective view of assembled apparatus 600 of FIG. 6G, with firstgripping portion 610 in slot 328 and second gripping portion 612 in slot330; FIG. 6J is a front perspective outline view of assembled apparatus600 of FIG. 6I; FIG. 6K is a top view of assembled apparatus 600 of FIG.6I; and FIG. 6L is a bottom outline view of assembled apparatus 600 ofFIG. 6I.

According to some example embodiments, apparatuses 600 may be scalablein size and the amount of force applied. Thus, there may be trade-offsbetween the size of the apparatuses 600 used and the number ofapparatuses 600 used (e.g., fewer bigger apparatuses 600 versus morenumerous smaller apparatuses 600). As would be understood by a PHOSITA,many factors may play into such a decision, such as length of outage,critical path considerations, physical limitations on access to weld 302c, etc.

According to some example embodiments, apparatuses 600 may be easilyinstalled, removed, replaced, or inspected. According to some exampleembodiments, apparatuses 600 may have a low profile (e.g., wheninstalled, not protruding from core shroud 300 by more than about 4inches or about 100 millimeters) so as to improve accessibility to weld302 c even if tie-rods associated with core shroud 300 are not removed.

According to some example embodiments, apparatuses 600 may be pre-loadedso as to prevent damage due to vibration, taking into considerationfactors such as irradiation relaxation and thermal tightening. Accordingto some example embodiments, apparatuses 600 may be pre-loaded toaccount for hoop stresses, such as normal, upset, and LOCA hoopstresses. According to some example embodiments, apparatuses 600 may bepre-loaded to account for pressure differences across core shroud 300,such as normal, upset, and LOCA differential pressures.

FIG. 7 is a flow chart illustrating a method for structurally replacinga cracked weld in a nuclear plant according to some example embodiments.

As shown in FIG. 7, a method for structurally replacing a cracked weldin a nuclear plant may comprise: obtaining an apparatus that comprises afirst body portion comprising a first gripping portion, a second bodyportion comprising a second gripping portion, a wedge portion betweenthe first and second body portions, and an adjustment portion, whereinthe first body portion is configured to slidably engage the second bodyportion, wherein the wedge portion is configured to exert a first forceon the slidably engaged first and second body portions, wherein theadjustment portion is configured to increase or decrease the first forceexerted by the wedge portion on the slidably engaged first and secondbody portions, and wherein when the adjustment portion increases thefirst force exerted by the wedge portion on the slidably engaged firstand second body portions, a distance between the first and secondgripping portions decreases (S700); forming slots on both sides of thecracked weld in a structure that includes the cracked weld, wherein theslots do not fully penetrate the structure (S702); disposing theapparatus near a surface of the structure so that the first grippingportion is in a first slot on a first side of the cracked weld and thesecond gripping portion is in a second slot on a second side of thecracked weld (S704); and using the adjustment portion to increase thefirst force exerted by the wedge portion on the slidably engaged firstand second body portions so as to decrease the distance between thefirst and second gripping portions until the first gripping portiongrips the first slot and the second gripping portion grips the secondslot with a second force that structurally replaces the cracked weld(S706).

FIG. 8 is a flow chart illustrating a method for structurally replacinga cracked weld in a nuclear plant according to some example embodiments.

As shown in FIG. 8, a method for structurally replacing a cracked weldin a nuclear plant may comprise: forming slots on both sides of thecracked weld in a structure that includes the cracked weld, wherein theslots do not fully penetrate the structure (S800); disposing a body neara surface of the structure, the body comprising a first end, a secondend, and a portion between the first and second ends, wherein the firstend comprises a first gripping portion, and wherein the second endcomprises a second gripping portion (S802); changing the body from anunflexed state in which the first gripping portion and the secondgripping portion are a first distance apart to a flexed state in whichthe first gripping portion and the second gripping portion are a seconddistance apart, wherein the second distance is greater than the firstdistance (S804); moving the body in the flexed state so that the firstgripping portion is in a first slot on a first side of the cracked weldand the second gripping portion is in a second slot on a second side ofthe cracked weld (S806); and changing the body from the flexed state tothe unflexed state so that the first gripping portion grips the firstslot and the second gripping portion grips the second slot with a forcethat structurally replaces the cracked weld (S808).

FIG. 9 is a flow chart illustrating a method for structurally replacinga cracked weld in a nuclear plant according to some example embodiments.As shown in FIG. 9, obtaining an apparatus that comprises a first bodyportion comprising a first gripping portion, a second body portioncomprising a second gripping portion, and an adjustment portion, whereinthe first body portion is configured to slidably engage the second bodyportion, wherein the adjustment portion is configured to exert a firstforce on the slidably engaged first and second body portions, whereinthe adjustment portion is further configured to increase or decrease thefirst force exerted on the slidably engaged first and second bodyportions, and wherein when the adjustment portion increases the firstforce exerted on the slidably engaged first and second body portions, adistance between the first and second gripping portions decreases (900);forming slots on both sides of the cracked weld in a structure thatincludes the cracked weld, wherein the slots do not fully penetrate thestructure (902); disposing the apparatus near a surface of the structureso that the first gripping portion is in a first slot on a first side ofthe cracked weld and the second gripping portion is in a second slot ona second side of the cracked weld (904); and using the adjustmentportion to increase the first force exerted on the slidably engagedfirst and second body portions so as to decrease the distance betweenthe first and second gripping portions until the first gripping portiongrips the first slot and the second gripping portion grips the secondslot with a second force that structurally replaces the cracked weld(906).

As would be understood by a PHOSITA, although the apparatuses andmethods for structurally replacing cracked welds of the presentapplication have been generally described with reference to core shroud300, the apparatuses and methods for structurally replacing crackedwelds of the present application are also applicable to other componentsin a nuclear plant, and to other components not in nuclear plants.

While example embodiments have been particularly shown and described, itwill be understood by those of ordinary skill in the art that variouschanges in form and details may be made therein without departing fromthe spirit and scope of the present invention as defined by thefollowing claims.

What is claimed is:
 1. An apparatus configured to structurally replace acracked weld in a nuclear plant, the apparatus comprising: a body thatcomprises a first end, a second end, and a portion between the first andsecond ends; wherein the first end comprises a first gripping portion,wherein the second end comprises a second gripping portion, wherein whenthe body is in an unflexed state, the first gripping portion and thesecond gripping portion are a first distance apart, wherein when thebody is in a flexed state, the first gripping portion and the secondgripping portion are a second distance apart, wherein the seconddistance is greater than the first distance, wherein when the body is inthe unflexed state, the body has a first shape, wherein when the body isin the flexed state, the body has a second shape, and wherein the firstshape is more curved than the second shape.
 2. The apparatus of claim 1,wherein the body comprises metal.
 3. The apparatus of claim 2, whereinthe metal is stainless steel.
 4. The apparatus of claim 1, wherein theportion between the first and second ends defines an access opening. 5.An apparatus configured to structurally replace a cracked weld in anuclear plant, the apparatus comprising: a body that comprises a firstend, a second end, and a portion between the first and second ends;wherein the first end comprises a first gripping portion, wherein thesecond end comprises a second gripping portion, wherein when the body isin an unflexed state, the first gripping portion and the second grippingportion are a first distance apart, wherein when the body is in a flexedstate, the first gripping portion and the second gripping portion are asecond distance apart, wherein the second distance is greater than thefirst distance, wherein when the body is in the flexed state, the firstgripping portion is configured to enter a first slot on a first side ofthe cracked weld in a structure that includes the cracked weld and thesecond gripping portion is configured to enter a second slot on a secondside of the cracked weld in the structure that includes the crackedweld, and wherein when the body is in the unflexed state, the firstgripping portion is configured to grip the first slot on the first sideof the cracked weld in the structure that includes the cracked weld andthe second gripping portion is configured to grip the second slot on thesecond side of the cracked weld in the structure that includes thecracked weld.
 6. The apparatus of claim 5, wherein the body comprisesmetal.
 7. The apparatus of claim 6, wherein the metal is stainlesssteel.
 8. The apparatus of claim 5, wherein the portion between thefirst and second ends defines an access opening.